Birthstone Guide: Tourmaline for Those Born in October

Tourmaline is the rainbow jewel of the gem world. No other gem is available in such an impressive array of colours. Paired with good durability and high lustre, this gemstone has become a favourite of many.

The hues, tones and saturations of tourmaline seem limitless, ranging from soft shades to vibrant explosions of colour. The desirability of the colour has a huge impact on price. The more vivid, rarer colours reach higher values, such as the coveted electric-blue copper bearing Paraiba tourmaline. Many tourmalines have commercial names such as rubellite for pink to red tourmaline. It is also common to describe them simply with the pre-fix of their colour i.e., 'pink tourmaline'.

Tourmaline is also known for its colour-zoned or "parti-coloured" specimens, where different zones of colour can be seen in the cross-section or down the length of the crystal. These can be cut to display the different colour patterns either as slices, creative carvings, facetted or cabochon gemstones, or left as whole crystal specimens. The most popular colour-duo is watermelon tourmaline which display pink on the inside and a rim of green on the outside.

Tourmaline is a complex boro-silicate of aluminium, magnesium and iron and the vast selection of colours are due to trace impurities and colour centres. The availability of these impurities may vary during growth, which allows for the development of different layers of colour. Its chemical makeup is so complicated that it cannot be synthesized, and is therefore always of natural origin.

The crystals are easy to identify with the tell-tale rounded 3-sided, or 6-sided, cross sections. They are often long and prismatic with heavy striations down the length of the crystal and are topped with either a pyramid or a flat pinacoid.

First discoveries have been attributed to both Brazil and Italy in the 1500's. The name of tourmaline was derived from the Sinhalese phrase tura mali, which was used by the miners and traders to refer to "unknown stones of mixed colours". The advancement of mineralogy allowed the recognition of tourmaline as its own gem species in the 1800's.

Tourmaline has a hardness of 7 - 7.5 and good toughness, making it suitable for use in jewellery. Inclusions are fairly common in tourmaline and many contain mirror-like fractures within them, which can be quite attractive, but may compromise the durability if knocked. Inclusion free stones are available and will fetch a premium price. Parallel needle-like cavities are also common in tourmaline, which in vast numbers can create chatoyancy, or the "catseye", effect.

Since their discovery, tourmalines have been used as talismans for protection against toxins and radiation as well as many other healing properties which are associated with particular colours of tourmaline. They are said to emit far-infrared rays that penetrate the body and stimulate and soothe the tissue within. This association is likely linked to the ability of tourmalines to become charged when heated, which is known as pyroelectricity.This property causes tourmalines to readily attract dust, and so a regular flick with a duster is recommended if they are displayed under hot lighting - arguably, a small inconvenience for such a stunner of a gem.

First published in the Spring 2018 issue of Gems&Jewellery, Christa Van Eerde MA MLitt DGA FGA explores the history of some of the world’s most magnificent pearls sourced in the Gulf region, including Bahrain, Kuwait and the UAE, famously regarded as the historic heart of the pearling world.

From Gems&Jewellery Spring 2018, Gem-A assistant tutor, Beth West FGA DGA, explores the remarkably epic journey of diamonds, and how their characteristic strength is rooted in their archaic origins and resilient survival.

Collectors, gem experts and jewellery lovers were buzzing with excitement in Geneva on May 15 when a whole host of incredible items hit the auction block. The three most prominent pieces – the Farnese Blue diamond and two 50 carat diamonds – soared far above their estimates to secure eye-watering prices.

Guy Lalous ACAM EG is on-hand to summarise some of the more in-depth articles from Gem-A's The Journal of Gemmology. Here, he explores an article on radiocarbon age dating of natural pearls from the Winter 2017 issue.

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With 2018 being the Year of European Cultural Heritage, Gem-A is excited to share Sarah Steele's important collaborative project between England and Spain to preserve and maintain traditional jet workings, which has recently been granted the European Heritage Seal.